1. Field of the Invention
The present invention relates to a reclining mechanism for a vehicle seat for adjusting an inclined angle of a back rest of the seat relative to a seat cushion.
2. Description of the Prior Art
Disclosed in Japanese Patent Laid-open Publication No. 8-52040 is a reclining mechanism for a vehicle seat which is composed of a pair of arm members for attachment to a frame structure of a seat cushion and to a frame structure of a back rest, the arm members being connected by means of a hinge pin for relative rotation about the hinge pin, a slide pawl slidably coupled with one of the arm members to be moved in a radial direction with respect to the hinge pin, and a cam element mounted on the hinge pin for rotation therewith and engaged with the slide pawl for maintaining the slide pawl in engagement with a ratchet portion of the other of the arm members and for disengaging the slide pawl from the ratchet portion when it is rotated with the hinge pin. In the reclining mechanism, the relative rotation of the arm members is restricted by engagement of the slide pawl with the ratchet portion to lock the back rest at an inclined angle and is permitted by disengagement of the slide pawl from the ratchet portion for adjustment of the inclined angle of the back rest.
In the reclining mechanism, the engagement of the slide pawl with the ratchet portion of the arm member is maintained in a condition where the slide pawl is pressed by engagement with a portion of the cam element. When the cam element is rotated with the hinge pin to disengage the slide pawl from the ratchet portion of the arm member, the slide pawl is retracted by engagement with a portion of the cam element. If the reclining mechanism is applied with a load, the slide pawl is slightly rotated due to an error in assembly of the component parts of the reclining mechanism. This results in looseness in engagement of the slide pawl with the ratchet portion of the arm member.
It is therefore a primary object of the present invention to provide a reclining mechanism for a vehicle seat wherein rotation of the slide pawl is prevented to firmly maintain the engagement of the slide pawl with the ratchet portion even if the reclining mechanism is applied with a load.
According to the present invention, the object is accomplished by providing a reclining mechanism for a vehicle seat, which comprises a first arm member for attachment to a frame structure of a seat cushion or a back rest of the vehicle seat, a second arm member for attachment to a frame structure of the other of the back rest or the seat cushion, the second arm member being connected with the first arm member by means of a hinge pin for relative rotation about the hinge pin and having a semi-circular ratchet portion concentric with the hinge pin, a slide pawl slidably coupled with the first arm member in a radial direction with respect to the hinge pin to be moved toward and away from the ratchet portion of the second arm member, and a cam element slidably coupled with the first arm member in a lateral direction perpendicular to the slide pawl and operatively connected with the hinge pin to be moved by rotation of the hinge pin in the lateral direction for engaging the slide pawl with the ratchet portion of the first arm member and for disengaging the slide pawl from the ratchet portion of the first arm member, wherein the hinge pin is loaded by a torsion spring assembled thereon to bias the cam element in the lateral direction for maintaining the slide pawl in engagement with the ratchet portion of the second arm member, wherein the slide pawl is formed at its outer end with a semi-circular toothed portion to be engaged with the ratchet portion of the first arm member and its inner end with a pair of laterally spaced projections for engagement with a flat end surface of the cam element, and wherein the cam element is formed at the flat end surface thereof with a pair of laterally spaced recesses to be engaged with the spaced projections of the slide pawl for permitting disengagement of the slide pawl from the ratchet portion of the first arm member.
In a practical embodiment of the present invention, the first arm member is formed with a first guide groove in a radial direction with respect to the hinge pin and a second guide groove perpendicular to the first guide groove, and the slide pawl is slidably coupled within the first guide groove while the cam element is slidably coupled within the second guide groove. For operative connection of the cam element with the hinge pin, the cam element is formed with an elongated lateral hole in the lateral direction perpendicular to the slide pawl, and the hinge pin is inserted across the lateral hole of the cam element for connection to the first and second arm members and being engaged with a portion of the lateral hole of the cam element.
According to an aspect of the present invention, there is provided a reclining mechanism for a vehicle seat, which comprises a first arm member for attachment to a frame structure of a seat cushion or a back rest of the vehicle seat, a second arm member for attachment to a frame structure of the other of the back rest or the seat cushion, the second arm member being connected with the first arm member by means of a hinge pin for relative rotation about the hinge pin and having a pair of diametrically opposed semi-circular ratchet portions concentric with the hinge pin, a pair of diametrically opposed slide pawls slidably coupled with the first arm member in a radial direction with respect to the hinge pin to be moved toward and away from the ratchet portions of the second arm member, and a cam element slidably coupled with the first arm member in a lateral direction perpendicular to the slide pawls and disposed between the slide pawls, the cam element being operatively connected with the hinge pin to be moved by rotation of the hinge pin in the lateral direction for engaging the slide pawls with the ratchet portions of the second arm member and for disengaging the slide pawls from the ratchet portions of the second arm member, wherein the hinge pin is loaded by a torsion spring assembled thereon to bias the cam element in the lateral direction for maintaining the slide pawls in engagement with the ratchet portions of the second arm member.
In a practical embodiment of the reclining mechanism described above, the slide pawls each are formed at their outer ends with a semi-circular toothed portion for engagement with each ratchet portion of the second arm members and at their inner ends with a pair of laterally spaced projections to be engaged with opposite flat surfaces of the cam element for maintaining the slide pawls in engagement with the ratchet portions of the second arm member, and wherein the cam element is formed with the opposite flat surfaces thereof with a pair of laterally spaced recesses to be engaged with the spaced projections of the slide pawls for permitting disengagement of the slide pawls from the ratchet portions of the second arm member.
In such an embodiment described above, it is preferable that a cam plate is assembled with the cam element to disengage the slide pawls from the ratchet portions of the second arm member by engagement therewith when the hinge pin is rotated against the load of the torsion spring to cause lateral movement of the cam element. The cam plate is formed with a pair of diametrically opposed cam slots which are engaged with a pair of cam pins provided on the slide pawls to disengage the slide pawls from the ratchet portions of the second arm member when the hinge pin is rotated against the load of the torsion spring to cause lateral movement of the cam element. In the embodiment, a movable cam plate may be assembled with the hinge pin to be rotated with the hinge pin and rotatably connected with the cam element to cause lateral movement of the cam element when rotated with the hinge pin, wherein the movable cam plate is formed with a pair of diametrically opposed cam slots which are engaged with a pair of cam pins provided on the slide pawls to disengage the slide pawls from the ratchet portions of the second arm member when the hinge pin is rotated against the load of the torsion spring.